TRIPOLI, March 21 (Reuters) - A runway at Libya's Tripoli airport was hit on Friday by a bomb planted there at night and then set off with a timer, not rockets as previously thought, the country's transport minister said.

"There was a small explosion," Abdelqadir Mohammed Ahmed told Reuters. Authorities closed the airport for several hours after the explosion. (Reporting by Reuters Television; Writing by Ulf Laessing; Editing by Mark Trevelyan)